Feeding device



Aug. 26, 1947. F.,L .'GREEN 2,426,200

FEED'ING DEVICE Filed oct. 9, 1941 'ATTORNEYS Patented Aug. Z6, 1947 FEEDING DEVICE Frank L. Green, Rockton, Ill., assigner to Green Manufacturing Co., Inc., Rockford, Ill., a corporation of Illinois Application October 9, 1941, Serial No. 414,256

A(Cl. 29-62l 4 Claims. l

This invention relates to feeding devices or fingers of the type used in automatic screw machines to grip the stock frictionally and push it for- Wardly, Heretofore, the gripping elements of such devices have been composed of rigid material such as metal and have well recognized limitations. For example the comparatively low coefcient of :friction necessitates high gripping pressures which are reduced by centrifugal force at high speed. Frequently, the stock surface is scratched by such fingers which must be exactly sizeddand shaped to correspond to the stock to e fe The primary object of the present invention is to provide a ringer which overcomes the limitations enumerated above.

A more detailed object is to provide a feed iinger in which the gripping surface is yieldable and distributes the gripping pressure evenly to the stock periphery.

Another object is to provide a linger having a gripping surface which adapts itself automatically to various stock shapes and which may be adapted to a comparatively Wide range of stock sizes by compression or expansion of the material of which the surface is composed.

A further objec-t is to provide for such size adjustment by axial compression of the gripping element.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which Figure 1 is a diametrical sectional view of a feed finger embodying the present invention and gripping a bar of work material.

Fig. 2 is a similar view with the finger adjusted for feeding a smaller size of stock.

Fig. 3 is a section taken along the line 3-3 of Fig. 2.

Fig. 4 is a similar section showing the finger gripping stock of non-circular cross-section.

Fig. 5 is a view similar to Fig. 1 showing a modication.

While the invention is susceptible of various modifications and alternative constructions, I have shown in the drawings and 'will herein describe in detail the preferred embodiment. It is to be understood, however, that I do not intend to limit the invention by such disclosure but aim to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

The improved feed finger as shown in the drawings comprises a tube 6 of resilient compressible material such, for example, as synthetic rubber confined both radially and axially in a casing 1 which is attachable in the usual way to the feed head 8 of a screw machine. While the tube may comprise a series of washers or segments arranged end to end or a series of annularly arranged strips, it is preferred to make it as an integral sleeve. Any yieldable material possessing the properties of softness and flowability combined with substantial resistance to wear may be used, including felt, felt impregnated with oil resisting rubber, or other material. Synthetic rubber of the so-called buna type has been found very satisfactory, one such material being formerly sold under the trade name of Kogene. Such materials are substantially unaffected by oils to which the feed fingers of automaticscrew machines are subjected in service use and are sufficiently tough and wear-resistant to withstand the frictional wear incident to such use.

A relatively soft oil resistant rubber is employed not only to facilitate adaptation of the internal or gripping surface lil to bars l0 of various sizes, but also to provide the proper degree of compressibility which results not only in size adjustability of the finger but in the distribution of the gripping force uniformly to all engaged parts of the stock periphery. Rubber having a hardness of about 45 measured by a Shore durometer has proven satisfactory. The degree of softness may be varied considerably especially for most eflicient action with different work materiale.

To confine the sleeve radially, the casing or shell 'l is a rigid metal tube having an internal diameter only slightly larger than the external diameter of the sleeve which may thus be inserted and removed readily and yet becomes confined by the shell after slight axial compression. In the form shown in Fig. l, one end of the shell has an inturned flange Il permitting the extension therethrough of stock of widely varying sizes and providing an abutment for one end of the sleeve. To prevent extrusion of the rubber from the flange opening I2 and around the stock I0, a rigid metal washer I3 is preferably interposed between the sleeve and the flange, the washer having a central opening i4 smaller than the opening in the flange and capable of receiving stock of sizes within the full range of adjustment of the sleeve. In Fig. l, the washer is the inturned flange of a ferrule or cup I5 which receives the end portion of the sleeve 6 and is sized to fit loosely in the shell. In the form shown in Fie. 5,

a simple washer is employed, this preferably being attached to the sleeve as by vulcanization of the rubber thereto so as to facilitate handling of the sleeve and its washers as a replaceable unit.

Means is provided for adjustably compressing the sleeve 6 axially within the shell l first to expand the sleeve into full contact with the inner shell wall I6 and then to `cause flowing of the rubber to reduce the internal diameter of the sleeve uniformly throughout its length and thereby vary the pressure with which the stock is gripped. Preferably, this means comprises a screw mechanism disposed below one end of the sleeve so as to minimize the overall radial dimensions of the nger. As shown in Fig. 1, screw threads I'I are formed in the end of the shell opposite the flange Il and receive an externally threaded tubular plug I8, the inner end of which is adapted to abut against the other end of the rubber sleeve which is covered by a ferrule I 9 providing a rigid end abutment 20.

By applying a spanner wrench to a hole 2l in the shell and a slot 22 in the plug, the sleeve mai7 be compressed endwise to contract the rubber around the stock with the desired gripping force. The plug has a central aperture 23 large enough to receive the largest size of stock with which the finger is to be used.

In the form shown in Fig. 1, the finger is mounted on the feed head 8 through the medium of a collar 24 screwed into a threaded hole 25 in the feed head, the collar being internally threaded to receive the end of the plug which projects beyond the shell 1,

In the modication shown in Fig. 5, the rigid abutment for the rubber body is indicated at 2S and disposed intermediate the ends of the shell 6, the wall of which is thickened at the end op-` posite the rubber body and formed with externalr threads 21 adapted to screw into the recess 25 of the feed head. The movable abutment for compressing the rubber axially within the shell comprises a hollow plug 28 screwed into a thread 29 formed in the opposite end of the shell. By removing the plug 28, the gripping element formed by the sleeve may be removed and replaced. The desired force for frictionally gripping the stock IE! is obtained by tightening the plug by means of a tool inserted in exposed slots 33.

In the use of the feed finger as above described, the stock to be fed is pushed through the finger after assembly of the same, as shown in Fig. l, the rubber sleeve 6 loosely receiving the stock. After the finger has been screwed into the head 8, the plug is screwed into the shell, as shown in Fig. 2, thereby compressing the rubber body. The latter, being confined against radial expansion by the cups l and I9 and by the shell, is contracted internally until the desired frictional gripping force is attained. The rubber is yieldabley or flowable and therefore adapts itself automatically to the external contour of the stock so as to grip all parts of the stock periphery uniformly regardless of whether the stock is of circular cross-section as shown in lFig. 3, or non-circular as shown in Fig. 4. By utilizing this property of owability, the internal diameter of the sleeve is adjustable over a substantial range of stock sizes. For example, a sleeve one inch long having a wall thickness of one-eighth of an inch will accommodate stock sizes varying in diameter to a range of more than one-sixteenth of an inch.

Because the gripping force exerted on the stock is distributed evenly over the stock periphery, the maximum unit pressure required to produce the desired gripping force is reduced to a minimum. This results in minimizing the wear on the gripping surface and correspondingly prolonging its service life. The yieldable character of the gripping surface is also advantageous in that abrasive particles carried on the stock surface are scraped off and do not become wedged in the fingers with sufficient force to cause scratching of the stock surface. Moreover, since the yieldable body is confined radially, the gripping force is not reduced by the centrifugal action incident to rotating the stock and lingers at high speed. A further advantage of the improved finger is that there is no tendency for the stock, when pushed forwardly against the feed stop, to rebound and thereby necessitate overfeeding as is required in certain cases with prior feeding devices. The service life of the improved feed finger is also increased, as compared to present fingers, by virtue of the fact that rubber inherently possesses a higher coefficient of friction than metal. Consequently, the radial gripping force required in order to produce a given feeding force on the stock is correspondingly less. Accordingly, it has been found in actual practice that the improved fingers will outwear the metal fingers of the types used heretofore and, in addition, is much less costly to manufacture. By virtue of its adiustability, simply by compression of the rubber, each replaceable rubber sleeve will accommodate a large number of sizes and shapes of stock and more sizes may -be handled simply by substituting in the same shell sleeves of differcnt internal diameters.

This application is a continuation in part of my application Serial No. 343,171, led June 29, 1940.

I claim as my invention:

l. A device for gripping a bar of stock to feed it endwise comprising a body of yieldable material adapted to receive and enclose said bar, means enclosing said body and applying endwise pressure thereto to maintain the body under a state of compression around said bar, and means on said enclosing means by which said device may be connected to the feed member of an automatic screw machine.

2. A device for gripping a bar of stock to feed it endwise comprising a shell defining an annular chamber around the bar, a sleeve of resiliently yieldable material completely filling said 4chamber, means for compressing said sleeve in an axial direction to place the entire volume thereof under compression and apply a uniform gripping pressure at all points of contact between the sleeve and the bar, and means by which said shell may be attached to the feed member of an automatic screw machine.

3. A linger for feeding stock in an automatic screw machine comprising a sleeve of yieldable flowable solid material such as oil resistant rubber adapted to receive a bar of stock, supporting means for said sleeve confining the latter against radial expansion, means for compressing the sleeve axially to reduce its internal diameter and cause a gripping pressure to be exerted on said bar, and means on said supporting means for attaching the linger to a feed member in an automatic screw machine.

4. A feed finger comprising a rigid walled shell adapted to be mounted on the feed element of an automatic screw machine and providing an internal cylindrical surface and internal abutments at opposite ends of said surface and facing toward and movable axially relative to each 2,426,200 5 other, means for urging one of said abutments REFERENCES CITED @Ward the other an@ a ,Sleevf of reslhently The following references are of reco'd in the yleldab-le materlal recelved 1n sald Shell between me of this patent: said abutments and adapted when compressed axially to expand externally against said sur- 5 UNITED STATES PATENTS face and form a contracted clrcumferentially con- Number Name Date tinuous internal surface of uniform cross section 1,941,999 Redmer Jan. 2, 1934 through the length of the sleeve. 2,071,138 Nolan Feb. 16, 1937 2,259,605 BaXendale Oct. 21, 1941 FRANK L. GREEN. 10 2,043,442 McNeil June 9, 1936 

